Standard Clauses for use in a California commercial lease providing a tenant with protection against a landlord's ability to pass through to the tenant increases in real estate taxes permitted under Proposition 13 because of a change in property ownership or the completion of new improvements during the lease term. These Standard Clauses also include an optional Proposition 13 landlord purchase option, which the landlord may require to provide Proposition 13 protections to the tenant. These Standard Clauses have integrated notes with important explanations and drafting and negotiating tips for both landlords and tenants.